Safety helmets currently used in the field of motorcycling, and the like, are provided with a chin strap which is fastened and adjusted in length in such a manner as to adhere to the user's throat and thus prevent accidental removal of the helmet from the user's head, above all in the event of a fall.
In particular, the chin strap is generally constrained to one lower end of the helmet and fastened permanently to the other lower end of the helmet by means of a fastening device.
As a rule, the chin strap is formed of two or more parts, which can be mutually constrained and adjusted by means of the fastening device, which is integral with one end of these parts.
Although specific reference has been made to safety helmets used in the field of motorcycling, as will be seen, the device according to the present invention can be utilised in general on all safety helmets used to protect the head of a user, for example of two-wheeled vehicles and the like, snowmobiles, and even more generally to fasten and adjust any strap used to mutually secure two flaps of a garment or personal accessory.
Over the years, numerous systems have been developed to fasten and adjust the length of the chin strap of helmets, such as those that provide for insertion of at least one portion of the strap, usually ribbon-like, inside two rings.
Although being very simple to produce, this system is not very intuitive and is complicated to use, due to the need to pass the strap through the two rings according to a pre-established order, when wishing to fasten the chin strap.
Moreover, once the ribbon-like strap has been inserted through the two rings, its free end must be suitably secured, for example by means of Velcro portions, or similar means, to prevent an annoying flapping effect.
Also known are chin strap fastening systems comprising a buckle, inserted into which is a complementary portion, structured in such a manner as to reach a position of coupling therewith. Unfastening of the device is achieved through the operation of a button, which causes release of the complementary portion from the buckle. This type of device, which substantially comprises a male portion and a corresponding female portion movable between two positions, a coupling position and a release position of the chin strap, does not allow fine adjustment of the length of the strap to be performed in a simple and rapid manner.
In this regard, there have been developed devices for adjusting and fastening the chin strap, provided with a ratchet pivoted inside a related casing and having one or more teeth adapted to engage a corresponding toothed portion which is provided on the chin strap.
Engagement of the toothed portion of the ratchet with that of the strap allows this latter to be fastened inside the device in such a manner as to prevent extraction of the strap from the device without first operating the ratchet.
At the same time, these devices allow the length of the chin strap to be adjusted through sliding of the toothing of the strap inside the casing of the device in different positions of engagement with the ratchet until reaching the desired position. This type of adjustment is known in the art as “micrometric” coupling as it allows fine adjustment of the length of the chin strap which offers a high level of adaptability to the various users of these straps.
In this type of device, the ratchet is usually maintained in a position of engagement with the strap by means of a spring and when wishing to extract the strap from the fastening device to allow the user to remove the helmet from his or her head, he or she acts manually on the ratchet causing it to move away from the position of engagement with the toothed portion of the strap, and therefore allow it to be unfastened and slide freely.
These devices suffer from some drawbacks related to the fact that, in order to be operated manually, the ratchet must project from the body, or casing, of the device, and this can lead to accidental and undesirable shifting of the ratchet from the position in which the chin strap is fastened.
In particular, it is possible for the projecting part of the ratchet to be lifted through accidental contact with external objects, such as possible contact with parts of the motorcyclist's jacket, or movements of the user which can unintentionally cause unfastening of the strap.
To overcome these drawbacks, in some cases the dimensions of the ratchet are reduced in such a manner that it does not project and a tape is constrained thereto to facilitate operation of the ratchet by the user when he or she wishes to unfasten the chin strap.
In other devices, release of the ratchet from the fastened position of the chin strap is carried out through the operation of a further lever pivoted to the casing of the device and coupled kinematically to the ratchet. In these devices, the ratchet is moved from the position of engagement with the strap by acting on a lever, which is structured and placed in a position of contact with the ratchet in such a manner as to be able to cause unfastening thereof from the strap.
A device of this type is described in the document EP-A-0772983 by the applicant EDC, in which the ratchet is operated in rotation to disengage the chin strap by means of a lever constrained in a rotatable manner to the casing of the device.
It must be noted that, although being provided with a lever which prevents direct operation of the ratchet, in the device described in EP-A-0772983, the operating lever and the ratchet are always in contact, and this means that, to prevent accidental operation of the lever from causing unfastening of the strap, the lever must be shaped in such a manner as to have a surface of engagement with the ratchet with an initial rotation, albeit for a short angular interval, which has no effect on the ratchet.
Moreover, coupling between ratchet and lever, both pivoted to the casing of the device, must have a certain degree of precision, which entails compliance with somewhat limited tolerances.
This means that, both due to the particular shape of the lever, and due to the considerably limited tolerances required, the device described in EP-A-0772983 is complicated to produce and therefore costly.
Moreover, this fastening device of the chin strap is of noteworthy dimensions, due to the need to produce a body of the device with dimensions such as to be able to constrain thereon both the ratchet and the operating lever.